1. Technical Field
The present invention relates to apparatus for use in dispensing viscous materials, such as dental compositions, and more specifically to syringes for dispensing viscous dental compositions in a controlled fashion.
2. Background Information
The practice of dentistry involves the use of various dental compositions which must be placed within small spaces located in cramped environments. When the composition has a low viscosity, it is a relatively simple matter to use a traditional syringe fitted with a tip having a small opening to provide precise control over the amount of composition dispensed and its placement.
Unfortunately, various dental compositions are quite viscous, and hence are difficult to force out of a conventional syringe. Others, such as resinous composite filling materials, are so highly viscous as to be virtually impossible to dispense using a conventional syringe.
In order to facilitate dispensing of viscous materials, two different tools have been developed, caulking guns and heavy-duty screw-type syringes. Both of these are capable of dispensing materials having a higher viscosity than may be dispensed from a conventional syringe.
Caulking guns and heavy-duty syringes are relatively expensive, so they are not considered disposable, although disposable tips are used to prevent the need to cleanse and sterilize tips for reuse with different patients. The remaining components of caulking guns and heavy-duty syringes must be cleansed and disinfected, however, thereby placing an unwanted burden upon the dental practitioner.
Because caulking guns utilize disposable tips, and because of the significant effort required to cleanse and disinfect them between uses, it is a standard practice to load them with enough material for use with several patients, to dispose of the tip after each patient, to affix a replacement tip, and then use the caulking gun with the next patient. Unfortunately, these devices are often splattered or otherwise contaminated during use by materials which have been in a patient's mouth. Although the splatter is rarely itself brought into contact with the mouth of a subsequent patient, and even though a dental practitioner typically uses fresh surgical gloves for each patient, it is not uncommon for the dental practitioner working on subsequent patients to touch the splatter as the caulking gun is manipulated during the course of the subsequent dental procedure, and then carry it into the patient's mouth.
Tips are not generally used with heavy duty screw-type syringes. Rather, the screw mechanism is generally used to advance material within the syringe so it can be manually removed. Not only is this subject to contamination similar in manner to the use of a caulking gun, but it is less convenient to use.
Even when using a caulking gun or heavy duty syringe, it has been found necessary to use a less viscous material than optimum in order to obtain flow. The lower viscosity formulation is thought to be weaker than a higher viscosity composite, resulting in premature failure of repairs made using a caulking gun or heavy duty syringe.
Several attempts have been made to avoid the problems of potential cross-contamination. For example, disposable syringes have been down-sized, so as to require less effort to dispense viscous materials. Many dental practitioners refuse to use these small syringes, however, because they are difficult to control when applying the strong force necessary to dispense viscous materials.
Because of the risk of infection when using caulking guns and heavy-duty syringes, and because of the difficulty of using small syringes, it is quite common for dental practitioners to forego the use of either of those devices in favor of a simple spatula or other similar tool. By way of example, this involves placement of a small quantity of composite material on a spatula and then manually packing the material into a prepared space within the patient's tooth. This is a time consuming process. In addition, small air pockets often remain within the packed material, thereby causing micro leakage to the interior of the tooth, or causing weakness in the repair. Either of these problems frequently result in premature failure of the repair. Yet, because of the problems of using other devices to dispense viscous material, many dental practitioners persist in the manual placement of viscous material using a spatula.
From the foregoing, it will be appreciated that it would be a significant advance if improved devices and associated methods for dispensing highly viscous materials could be developed for use by dental practitioners.